Type II restriction endonucleases from Helicobacter pylori include an enzyme with a novel recognition sequence.

Type II restriction endonuclease activities of Helicobacter pylori strain Roberts and of the type strain H. pylori NCTC 11637 were detected and analysed by conventional techniques. The endonucleases were partially purified, their optima for activity and their recognition and cleavage sites were determined. H. pylori (Roberts) contained at least two enzymes: HpyBI was an isoschizomer of RsaI (GT/AC) and HpyBII was of a novel specificity (GTN/NAC). H. pylori NCTC 11637 was found to contain an isoschizomer of EcoRV (HpyCI: GAT/ATC) and at least one other enzyme which was too unstable to characterise.